//禁用F5刷新
document.onkeydown = function (e)
{
    e = window.event || e;
    var k = e.keyCode;
    //屏蔽ctrl+R，F5键，ctrl+F5键  F3键！验证
    if ((e.ctrlKey == true && k == 82) || (k == 116)
        || (e.ctrlKey == true && k == 116)||k==114) {
        e.keyCode = 0;
        e.returnValue = false;
        e.cancelBubble = true;
        return false;

    }
}